The preservation and storage of biological materials (e.g., mammalian cells) at room temperature, while maintaining the viability of the biological material, is a long unrealized goal. Existing methods available for preservation and storage of biological materials include cryo-preservation and dehydration. The use of protectant substances to enhance the viability of the biological material after recovery from storage is prevalent in both cryo-preservation and dehydration.
Cryo-preservation involves cooling the biological material to temperatures which arrest the material's biochemical and chemical processes. Preservation is maintained as long as the temperature is maintained at sufficiently low values. Cryo-preservation is currently the only technique proven to preserve mammalian biological material while maintaining the material's viability. However, cryo-preservation has its drawbacks and limitations. Cryo-preservation is expensive and limits the transportation of biological materials to locations where the required temperature may be maintained.
Dehydration involves removing water (desiccation) from the biological material in order to dramatically limit or arrest the material's biochemical and chemical processes. The storage temperature of dehydrated biological material may be above cryogenic temperature or at room temperature if the degree of drying is sufficient to arrest processes at this temperature. The extent of dehydration required may be extreme. Freeze-drying is an example of the dehydration method, wherein biological material is cooled to a temperature where ice forms and then the sample is subsequently dried under vacuum.
The dehydration of biological material suffers from a major limitation in long-term storage at ambient conditions: the degradation of the biological material by cumulative chemical stresses encountered as the vitrification solution gets concentrated in the extra-cellular space. This results in irreversible cell damage before the cells and the vitrification solution can reach a suitably low moisture content to become glassy. The degradation occurs regardless of the drying mode employed (dry-box, vacuum, etc).
U.S. Pat. No. 6,808,651 discloses a method for creating a thermoplastic shaped-body by concentrating a trehalose solution. The trehalose solution is concentrated by heating it to a temperature of at least 165° C. in order to reduce the solution's water content. However, there is no mention of using trehalose to aid in the preservation of any type of biological material. Additionally, in the present invention, heating a biological composition to a temperature in excess of 50° C., let alone 165° C., will almost certainly cause irreversible damage to the biological material contained within the composition and render it non-viable.
The use of microwaves to aid in the dehydration of biological material has met with little success. Microwave processing using non-ionizing electromagnetic radiation can actively induce the evaporation of polar molecules like water from a sample of biological material. The vibration of polar molecules in a constantly changing electrical field of microwave radiation rapidly increases the temperature of the sample. The rapid increase in temperature has numerous adverse biological effects and results in a non-viable sample.
The article, Making Monosaccharide and Disaccharide Sugar Glasses by Using Microwave Oven, published in the Journal of Non-Crystalline Solids, Volume 333, Issue 1, 1 Jan. 2004, Pages 111-114, discloses a method for making sugar glass without caramelization of the sugar through the use of microwaves. Additionally, the article discloses the desire to use sugar glass to conduct physical aging studies and study relaxation dynamics because of the high glass transition temperature of the sugars. The article demonstrates the utility of microwave radiation as a means to quickly remove water from materials. While the article does disclose some of the protective characteristics of trehalose on proteins and biomembranes, there is no mention of using microwave radiation on a variety of vitrification agents, including trehalose, for the preservation and storage of biological materials above cryogenic temperature, while maintaining the viability of the biological material.
A technology that facilitates dry storage of biological material above cryogenic temperatures would greatly bolster efforts in cellular and tissue engineering, cell transplantation, and biosensor technology. Hence, there exists an unsatisfied need for a composition and method to preserve and store biological materials above cryogenic temperature while maintaining the material's viability.